Carrier for integrated circuit

ABSTRACT

A carrier having a plurality of leads extending from the lateral sides thereof. The leads extending along the lateral side and over protuberances into depressions in the bottom of the carrier. Each of the depressions is separated by ribs from the other depressions. The ends of the leads disposed in the depressions are prevented from substantial movement by the rib to prevent contact with adjacent leads. At least some of the leads are provided with holes disposed adjacent to the exit of the leads from the enclosure of the carrier. The holes in the leads allow the leads greater flexibility at their portions close to the entrance of the leads into the enclosure. The leads are tapered along their length toward the protuberances. Further, the leads are separated by a width along the lateral side which is within the range of slightly greater than the width of the leads to less than the width of the leads to prevent nesting.

This application is a continuation of application Ser. No. 286,833,filed July 27, 1981.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a carrier for integrated circuits. Moreparticularly, this invention relates to a carrier for integratedcircuits which provides for each lead to extend over a protuberance toan end thereof in a depression to prevent the leads from movement duringshipment, installation, and/or use.

2. Description of the Prior Art

An appreciable factor in the cost of fabrication of semiconductorpackages and particularly those packages embodying integrated circuitsis involved with the package or carrier. The common dual in-line package(hereinafter referred to as DIP) has a basic rectangular shape. Theleads extend outward from the longer sides of the rectangular shape andthen at right angles to below the bottom of the DIP package. As theintegrated circuit has increased in functionality and with the movetoward smaller geometries increases it is desirable that more and moreconnections be available to and from the integrated circuit. This hasresulted in an increased number of leads. The DIP packages became longerproviding more space along the longer sides of the rectangular shape forthe increased number of leads.

The ends of the leads extending from the DIP package are not constrainedand therefore are subject to being moved laterally into contact withother leads. This can lead to breakage of the lead or increasedinstallation costs because the lead must be straightened prior to itsinstallation in, for example, a printed circuit board.

None of the prior constructions show a carrier which provides amechanism for constraining the leads extending from inside the carrierby placing the end of the leads outside the enclosure of the carrierwithin depressions in the bottom thereof.

SUMMARY OF THE INVENTION

The present invention involves a carrier for semiconductor devices, forexample, integrated circuits. The carrier includes an enclosure which iscapable of containing and sealing an integrated circuit therein. Thecarrier has a plurality of leads which extend from adjacent theintegrated circuit outward and through the lateral sides of the carrier.Each lead is connected through a typical bonding technique to oneinput/output pad of the integrated circuit. In other words, the leadsconnect the integrated circuit within the enclosure to the outsideworld. The leads connect the integrated circuit to its power supply andprovide the necessary input/output connections for allowing theintegrated circuit to function.

The enclosure of the carrier has a top and bottom and four lateralsides. However, it should be noted that although a square space as shownherein any convenient shape can be utilized, for example, a circular orrectangular shape. The top and bottom of the enclosure are approximatelyparallel and coextensive. The sides comprise two pairs of opposite,parallel lateral sides. The lateral sides extend from the top to thebottom and at each end to a lateral side of the other pair. Variouscorners, etc., for example, a rounded corner or a beveled corner, can beprovided between adjacent lateral sides.

Each of the leads connected to the integrated circuit extends from itsend adjacent to the integrated circuit through a lateral side of theenclosure. The lead then extends along and approximately parallel to thelateral side toward the bottom. For each lead, a protuberance which isparallel and coplanar with the lateral side is provided. The leadextends around the protuberance and into a depression in the bottom ofthe enclosure. The depression in the bottom of the enclosure whichreceives the end of the lead prevents that end from contact with otherobjects and substantially constrains the lead from lateral movement andcontact with its adjacent leads. The protuberance has a first slope incoplanarity with its associated lateral side. The protuberance has arounded end from the first slope to a second slope, which has an angleof approximately 25° with respect to the lateral wall and extends fromthe rounded end of the protuberance into the depression in the bottom ofthe enclosure.

The protuberances can be arranged to form a continuous projection alongthe lateral wall extending beyond the bottom of the carrier. As shownherein, this projection is notched to provide the protuberancesdiscussed. The end of the lead within the depression extends below thebottom and thus is prevented from contact with any other objects. Thisallows the lead to be thinner because less rigidity and strength isrequired. Also, the ends of the protuberances can be various shapes suchas flat with sharp corners. With the end of the lead outside theenclosure so constrained by the depression in the bottom of theenclosure, increased reliability is obtained because it is less likelythat the lead will move laterally. Therefore breakage of the leads dueto lateral movement and the risk of the leads contacting one another toproduce a short is reduced.

At least some of the leads are provided with holes adjacent the point ofexit from the enclosure. The holes allow the lead greater flexibility toreduce the strain on the solder connections to a printed circuit boardas the board's dimensions change due to thermal effects. The leads havea width along the lateral side which is slightly less than, equal to, orgreater than the distance between leads. This prevents nesting of leads,if two carriers come into contact. Nesting occurs when a lead of onecarrier inserts between adjacent leads of another carrier. The leads aretapered adjacent the protuberances to a portion having a reduced widthwhich extends over the protuberances into the depression.

It is an advantage of the present invention to provide a carrier for anintegrated circuit having improved shipment capabilities.

It is a further advantage of the present invention to provide a lighterweight carrier which utilizes more of the peripheral surface area forlead placement to reduce the size of the carrier.

It is another advantage of the present invention to provide a carrierhaving reduced size and lower cost.

It is an advantage of the present invention to provide reduced strain onsolder connections by utilizing holes in the lead to increaseflexibility.

It is another advantage of the present invention to provide leads whichhave width approximately equal to or greater than the distance betweenthe leads to prevent nesting.

An additional advantage of the present invention is to provide thinnerleads for weight reduction and reduced lateral spacing by constrainingthe end of the lead outside the enclosure containing the integratedcircuit within a depression in the bottom of the chip carrier.

It is also an advantage of the present invention to provide lateralstability for the ends of the leads outside the chip carrier containingthe integrated circuit by placing the ends of the leads within adepression in the bottom of the chip carrier with each lead beingprovided with its own individual depression.

It is also an advantage of the present invention to provideprotuberances under the leads to reduce solder wicking in this area andprevent solder bridging during reflow of the solder for printed circuitboard attachment.

It is also an advantage of the present invention to provideprotuberances under the lead to support the lead and limit leaddistortion from forces bringing the carrier into contact with otherobjects during circuit board attachment, socketing, testing, or generalhandling.

It is also an advantage of the present invention to provideprotuberances under the leads to prevent solder wicking in this areaduring printed circuit board attachment by solder dipping techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of the integrated circuit carrier of the presentinvention with portions broken away to reveal internal details (not toscale);

FIG. 2 is a bottom view of the chip carrier of the present invention;

FIG. 3 is a side view of the chip carrier of FIGS. 1 and 2;

FIG. 4 is a cross-sectional view taken along section line 4--4 of FIG.2;

FIG. 5 is a cross-sectional view, on a slightly enlarged scale, takenalong section line 5--5 of FIG. 2; and

FIG. 6 is a partial view of a carrier showing a side view of twoadjacent leads.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The carrier 20, as shown in FIG. 1, has a basically square shape. Thecarrier 20 includes an enclosure 22 and a plurality of leads 24. Theleads can be constructed of an electrically conductive metallicmaterial, for example, copper alloy. The enclosure 22 can be constructedfrom plastic, for example, epoxy plastic. The chip carrier can be of anyconvenient shape, however, as shown in FIGS. 1, 2 and 3, it has agenerally flat box shape with a top 26, a bottom 28, and four lateralsides 32 through 35 with top 26 and bottom 28 square and lateral sides32 through 35 rectangular shape. A portion of the top 26 in FIG. 1, hasbeen broken away to reveal an integrated circuit 29 attached to theleads 24 by a plurality of fine bonding wires 40.

All of the leads 24 are similar and a discussion of a particular lead 43shall suffice for all. One end 45 of lead 43 is located adjacent tointegrated circuit 29 and is connected thereto by one of the bondingwires 40. Lead 43 extends through lateral side 34 (as shown in FIG. 3)at approximately half of the distance between the top 26 and the bottom28 of the enclosure 22. The lead 43 has flat side 47 (FIGS. 3 and 5).

The corners connecting the lateral sides 32 through 35 can be anyconvenient shape such as rounded, sharp, or beveled. Lateral sides 32and 34 form a pair of lateral sides which are parallel and haveapproximately the same dimensions. Lateral sides 33 and 35 form a pairof lateral sides which are parallel and also have approximately the samedimensions.

Lead 43 extends from its end 45 within the enclosure 22 out lateral side34 (as shown in FIG. 3) and extends along lateral side 34 toward bottom28 with flat side 47 thereagainst. All the leads 24 exit the enclosureat approximately the midpoint between the top 26 and the bottom 28 withflat side 47 thereagainst. The bottom 28 (as shown in FIG. 2) isprovided with a plurality of depressions 50. Each depression isseparated from the other depressions by a portion of the bottom 28 whichis at the same level as the remainder of the bottom. Specifically asshown herein, the separating portion is slightly above the remainder ofthe bottom, although it can be lower than the remainder. Also, theprotuberance can have the same level as the bottom if deeper depressionsare provided. The leads 24 extend to an end located in the depressions50 as shown in FIG. 2.

In FIG. 3, the leads 24 are shown extending along the lateral sides overa plurality of protuberances 53. The protuberances 53 can be arrangedalong each lateral side to form a single projection which extends beyondthe bottom 28. The protuberances have one slope side which is coplanarwith the lateral side from which it extends. Each lead extends over itsassociated protuberance into one of the depressions 50. One of thedepressions 50 is associated with each of the protuberances which inturn is associated with one of the leads.

As shown in FIG. 4, each of the leads 24 extends over a projection 53into a depression 50. Each depression is separated by a portion of thebottom which is at approximately the same level as the bottom (butslightly above) which forms ribs 56. The ends of the leads 24 are thussubstantially constrained from movement parallel to the plane of thelateral side, through which it extends, by the ribs 56. The rib 56 thussupports leads 24 and prevents adjacent leads of leads 24 from cominginto contact. Since the ribs provide support against lateral movement,the leads can be constructed of a thinner material.

Lead 43, as shown in FIG. 5, extends over its associated protuberance 58with flat side 47 thereagainst. Protuberance 58 is similar to the otherprotuberances 53 and a detailed discussion of one protuberance shallsuffice for all. A slope 60 of protuberance 58 has coplanarity with thelateral side 34. The lateral side 34 may have a small slope from itsmidpoint to its connection with bottom 28 of, for example, approximately3°. The protuberance extends from slope 60 through a rounded end 62. Aslope 64 of protuberance 58 extends from rounded end 62 into adepression 66 which is one of the depressions 50. The slope 64 has anangle of approximately 25° with respect to the lateral side 34. Theslope 64 extends toward bottom 28 and away from lateral side 34 andgenerally toward lateral side 32 (FIG. 2).

Lead 43 is shown in FIG. 5 in two positions. First, lead 43 (as shown bythe broken line) is bent over rounded end 62, then a punch 68 (shown bythe broken line) contacts the portion of the lead extending beyondrounded end 62. The punch 68 (shown at its second position by a solidline) forces the lead to deform and move angularly to a positionadjacent to slope 64 (shown by a solid line). The end 70 of lead 43 isnow disposed within depression 66. The end 70 is prevented from lateralmovement by ribs 73 and 74 (FIG. 2) of ribs 56. The corners 76 of bottom28 are also raised to provide the ribs, for example, rib 74 in FIG. 2.

If force is applied to pull lead 43 away from slope 60 and lateral side34 of enclosure 22, the end 70 and the portion of lead 43 adjacentthereto contacts slope 64 to prevent such movement. After deformation bypunch 68, flat side 47 does not move away from slope 60 as a result of aspring-back action after deformation since end 70 contacts slope 64. End70 is protected from contact with other objects by being disposed withindepression 66. The ends of the other leads 24 are also protected withintheir respective depressions 50.

In FIG. 5, the punch moves from its first position at the right (asshown in FIG. 5) toward the second position (as shown in FIG. 5). Thiscauses lead 43 to bend around and over rounded end 62 and into contactwith or close proximity to slope 64. The lead 43 deforms and, even afterpunch 68 is removed from contact with lead 43, the end 70 remainsclosely adjacent to slope 64 with flat side 47 thereagainst.

The enclosure 22 has beveled edges 79 and 80 (FIG. 1) which are usefulin aligning the carrier for proper connection of the leads to, forexample, a printed circuit board.

As shown in FIG. 6, adjacent leads 100 and 102, which are two of leads24, extend from enclosure 22. Leads 100 and 102 have openings or holes106 and 108, respectively, located therein close to the exit of theleads out of enclosure 22. The holes as shown are rectangular; however,any convenient shape can be utilized. The holes provide increasedflexibility to the leads. The leads 100 and 102 extend to downward (asshown in FIG. 5) to thinner portions 120 and 122, respectively. The lead100 has tapered edges 110 and 112 to thinner portions 114 and 116. Thethinner portions 120 and 122 extend over protuberances 130 and 132 intotwo of the depressions 50 (not shown in FIG. 6). The leads 100 and 102can be attached by soldering to a printed circuit board 200 at the lowerportion 136 and 138, respectively, over their respective protuberances.

When leads 100 and 102 are soldered to contact pads 202 and 204,respectively, of printed circuit board 200, lower portions 136 and 138are in contact with contact pads 202 and 204. The solder 206 is attachedto thinner portions 120 and 122 (only a portion of the solder is shownattached to lead 102). The solder can be applied to the leads on eitheror both sides of the thinner portions 120 and 122 from the contact atlower portions 136 and 138, respectively, with the printed circuit board200. Soldering can be by reflow, dipping, wave, or other appropriatetechniques.

The protuberances 130 and 132 provide support to the leads 100 and 102,respectively, when the contact is made with the printed circuit board orany other object, for example, another carrier during shipment or duringinsertion into a socket. The socket can provide for contact with theleads between the tapers and the entrance of the leads into theenclosure along the lateral sides of the enclosure 22. The protuberances130 and 132 also limit the amount of solder which can accumulate betweenthe leads 100 and 102, and enclosure 22 as a result of a wicking actionto prevent the solder 206 from bridging between the adjacent leads 100and 102.

The holes 106 and 108 allow the leads 100 and 102 to flex forcompensating for changes in the dimensions of the printed circuit boarddue to thermal effects. The leads 100 and 102 are separated by an area140. The distance across the area 140 between leads 100 and 102 isapproximately equal to the width of lead 100. The lead 102 has a widthapproximately equal to lead 100. The width of the leads can exceed thespace separating, i.e., area 140 or be slightly less than if the leadsare not perfectly parallel. Thus, the width of area 140 can be slightgreater than, equal to, or less than the width of lead 100. Theserelative widths provide a spacing between leads which prevents a lead ofanother carrier (not shown) similar to carrier 20 from fitting ornesting between leads 100 and 102. The nesting can cause damage to theleads especially in automatic processing operations.

Whereas the present invention has been described in particular relationwith the drawings attached hereto, it should be understood that otherand further modifications, apart from those shown or suggested herein,may be made within the scope of this invention.

What is claimed is:
 1. A carrier for an integrated circuitcomprising:(a) an enclosure having a top and a bottom parallel to saidtop, and two pairs of opposite parallel lateral sides connected togetherand extending from said top to said bottom, at least one lateral sidehaving a plurality of protuberances extending beyond said bottom, saidbottom having depressions therein, each depression located adjacent oneof said protuberances; each protuberance having a rounded end extendingaway from said one lateral side toward said bottom and a slope extendingfrom said rounded end into its adjacent depression, and (b) a pluralityof leads, each lead having one end disposed in said enclosure andextending through said one end lateral side over and substantiallyabutting said rounded end into said adjacent depression along andsubstantially abutting said slope for support to another end opposite tosaid one end of said lead.
 2. A carrier having an integrated circuitcomprising:(a) a sealed enclosure having said integrated circuit twodisposed therein and provided with one side and another adjacent sideand having a plurality of protuberances extending from said one side;and (b) a plurality of leads extending from said one side of saidenclosure, each lead separated from any other lead and having one endlocated within said enclosure, each lead extending adjacent said oneside to said another side over and substantially abutting one of saidprotuberances for support to another end of said lead opposite to saidone end thereof.
 3. A carrier comprising:(a) an integrated circuit; (b)a plastic enclosure enclosing said integrated circuit and having firstand second parallel sides of approximately equal dimensions, two pairsof parallel lateral sides extending between said first and secondparallel sides at right angles thereto, each lateral side of one pair oflateral sides extending from one side of another pair of lateral sidestoward another side of said another pair, each lateral side having aplurality of protuberances, said second side having a plurality ofdepressions, each depression located adjacent a protuberance, eachprotuberance having a first slope extending beyond said second sideparallel and coplanar with said lateral side, a rounded end extendingfrom said first slope toward its opposite parallel side, and a secondslope extending from said rounded end toward said second side and theopposite lateral side into said depression adjacent thereto; and (c) aplurality of metallic electrical leads, each lead having one end withinsaid enclosure and extending out of said enclosure through one of saidlateral sides, parallel to said lateral side toward said second side,over said rounded end of said protuberance, and substantially abuttingsaid second slope for support to another end opposite to said one endthereof within said depression to prevent said second end from parallelmovement relative to said lateral side.